1. Field of the Invention
The present invention relates to a correcting process of an image picked-up by an image sensor, and in particular, relates to an extracting and correcting process of point defects generated by a defective pixel or a abnormality of dark current characteristics of an image sensor.
2. Description of the Related Art
In recent years, there have been concerns about the increase in a defective pixel which outputs a defective pixel signal called a point defect as a result of an increase in the pixel number of an image sensor used by a digital camera. The point defect is generated according to leak by a structural failure of the pixel and a abnormality of dark current characteristics. There is a point defect which is generated regardless of an exposure time or a sensitivity setup and a point defect to which the necessity for correction comes out according to a shooting condition.
The following method is proposed as a correction process for data of the point defect. For example, in Japanese Patent Laid-Open No. 2000-209506, black level data picked-up by the same exposure time as the exposure time at the time of a usual shooting is obtained, and the pixel which exceeds a predetermined level in the black level data is determined to be a point defect pixel. The position of the determined point defect pixel is stored, and data of the stored point defect pixel is corrected at the time of the usual shooting.
Also, in Japanese Patent Laid-Open No. 2000-59690, the data of the defective pixel is corrected based on position information of the defective pixel beforehand stored for a shooting image of a short exposure time. The defective pixel is detected for the shooting image of the long exposure time, and the data of the defective pixel is corrected based on the detection result.
However, with respect to the correction number of the point defect, there is a limit by restrictions of a cost and a system by a memory capacity, a correction time, etc. Since the generation state of the point defect changes according to a shooting condition, suitable correction of the point defect cannot be performed. Additionally, in a defect detection process of a usual production process, it is impossible to set up all the generation states for obtaining the correction data because of a process time, a restriction of memory capacity, etc. For the above reason, in cases where a user used an imaging apparatus in environments other than the presumed general operating environment, it is difficult to efficiently correct the point defect generated in the user's operating environment.